Well drilling apparatus



Oct. 6, 1964 D. B. GRABLE WELL DRILLING APPARATUS 2 Sheets-Sheet l Filed March 17, 1961 Oct. 6, 1964 Filed March 17, 1951 isla' 2 2 Sheets-Sheet 2 I 57 4e 4&- I g 49/ l 5l l 40 l N I 2| 1 5o 22 I i l l 1 as 54 r4o F,32 28 9 3 al )3 7 z 33 HT:

45 INVENTOR.

Dorval/Aw B. 62p E l "v/ I [Q ATTORNEYS" United States Patent O 3,151,690 WELL DRILLING AFPARATUS Bonovan B. Grable, Long Beach, Calif., assigner to Gas Drilling Service Co., Los Angeles, Calif., a copartnership Filed Mar. i7, 1961, Ser. No. 96,557 i8 Claims. (Ci. 175-'52t) This invention relates generally to improvements in a known particular type of well drilling practice employing a dual pipe string made up of inner and outer annularly spaced pipes forming between them an injection iiuid pas'- sage, and the inside pipe a return iiuid passage through which cuttings from a bit carried by the lower end of the string are carried to the ground surface by fluid circulated through the passages. While in its broad aspects, the invention contemplates utilization in the manner hereinafter explained, of any suitable cutting-entraining fluid, my preferred practice is to effect air entrainment of the cuttings by delivery of compressed air to the inter-pipe injection passage.

The cutting removal efficiency in this type of drilling is dependent upon a number of factors including air circulation rates, passage Siles or areas, and proper direction of air flow at the bit where the cuttings are entrained. These requirements are known. Another factor, productive of difficulties in the past, involves possible interference with the air passage about the bit by conditions in the well such as low formation pressure, or high formation porosity, permitting the escape of the working air into the formation, as well as reduction of the compressed air pressure below a level required for the maintenance of effective entrainment velocities. In addition to these conditions, there may be other unfavorable circumstances such as caving tendencies of the formation about the bit, and the presence of liquid in the hole in quantities or rates of in-flow from the formation, as to interfere with proper air circulation, where the drilling occurs in a formation where there is water or oil intrusion.

My general object is to provide certain simple and eective expedients for isolating the bit and cutting entrainment from the stated adverse well conditions, to a degree that will assure continuous and effective entrainment of the cuttings without serious air pressure loss, or interference by other physical impediments in the well. This objective is accomplished by the maintenance of a pressure or sealing barrier between the entrainment locus and the formation and well bore at the outside, all in a manner to close about the bit against the bottom hole formation and to maintain that closure progressively as drilling proceeds.

Structually, the invention contemplates applying to a bottom section of the dual pipe drill string (or to a correspondina sub, mandrel or the like which is considered a portion of the pipe string) to which the bit is attached, a tubular barrier sleeve or shroud which engages the formation about the bit and advances therewith as the hole deepens. As will appear, particular benefits are gained by accommodating the tubular shroud for vertical movement relative to the drill bit so that depending upon the hardness and penetrability of the formation, the shroud may itself advance somewhat ahead of the bit in more easily penetrable formations, while in hard formation drilling the shroud may bottom at about the cutting depth of the bit.

Where the tubular shroud is designed for cutting of the formation about the bit, the shroud is mounted for rotation with the bit so as to be positively rotatable under the iniiuence of downward force exerted on the cutting end of the shroud as by spring thrust or weighting of the shroud, all as will later appear.

3, l 5 l ,dhd Patented @et 6, 1954 rice lt is also contemplated that if desired, the shroud sleeve may be permitted to remain rotationally stationary during the rotation of the pipe string and bit, as when the shroud may tend without rotation, to penetrate a soft sand formation, although in this instance l preferably provide for selective driving connection between the pipe string and shroud so that the latter may be positively rotated under conditions requiring its rotation.

For the purpose of relieving the cutting entrainment locus from interference by excessive oil or water intrusion or the presence of a disturbing hydrostatic column in the well, provision is made for packing off the tool assembly against the formation above the bit. As will appear, such pack-off may occur about or above the shroud, although maintenance of a seal carried by the shroud itself is preferred.

All the features and objects of the invention, as well as the details of certain typical and illustrative embodiments, will be understood more fully from the following detailed description of the accompanying drawings in which:

FIG. l is a general view partly in longitudine. section showing the apparatus in drilling position within a well;

FlGS. 2 and 2a are enlarged composite showings mainly in longitudinal section, of the drill bit and shroud assembly of FIG. l;

FiG. 3 is a View similar to FIG. 2 but showing the parts in changed positions;

FIG. 4 is' a cross section on line 4 4 of FIG. 2; and

FIG. 5 is a view partly in section showing a variational embodiment of the invention.

Referring first to the general showing of FIG. l, the well drillin'7 tool assembly indicated at iii is shown to be carried on the lower end of a pipe string il which may be made up in any of the known methods to comprise inner and outer pipes il?. and i3 annularly spaced to provide an injection passage 14 through which a cuttingentraining uid is directed downwardly to the drilling locus of the bit, as will presently appear. As previously indicated, l preferably use as the drilling duid, air discharged at suitable pressure, usually in the order of several hundred p.s.i., by compressor 1S through line 16 leading to passage i4. in drilling some formations, it may be desirable to introduce with the compressed air, an additive adapted to affect the formation being drilled, or the condition of the bit cuttings. As illustrative, I may introduce through. line r6 any of the well known foaming agents having the property of formation penetrability and the capacity of aiding in the entrainrnent of cuttings. Such foaming agents also may be used in the presence of excessive water, by reason of their tendency to increase the liquid entrainment rate in a circulated gas stream. As will appear, the cuttings formed by the bit are entrained in the injected air stream and conducted to the ground surface through passage i7 in the inner pipe 12.. if for any reason it may be desirable to pressurize the well bore outside the pipe string 1l, a pressurizing gas may be introduced through line i3 below packing head 19 of the casing 20, through which the dual pipe string is supplied and lowered as drilling proceeds.

The drilling tool assembly, generally indicated at 19, is shown to comprise a sub or mandrel 2i connected to the lower end of pipe 13, and an internal pipe 22 connected to pipe l2, these pipes being annularly spaced to form a continuation passage 2.3 of the injection passage iid,V passage 24 in pipe 22 similarly being an extension of passage l?. As previously indicated, the assembly of mandrel 21 and pipe 22 may be regarded as parts or continuations of the dual pipe string il. A conventional dri bit having cutters 25 is connected to the lower end of the pipe string as by threading its pin end 2.6 into box 27 of the drill bit body 28. The latter is shown to contain fluid end of pipe 22.

circulation passages 29-and a bore 39 which receives the lower reduced end 3l of a tubular adapter 32 containing a bore 33 which receives inside the seal rings 34 the lower Duringv drilling, compressed air is discharged from passage 23 Vthrough the annular passage 134 into passages 29, thence to be directed against and about the cutters 25 so as to entrain the cuttings in the air stream being Vreturned to the ground surface through passages 37 and 24.

The tool assembly Valso comprises a tubular sleeve or shroud 38 which functions to maintain a pressure barrier between the formation and interior of the well, and the bottom Vof the bore hole being drilled. The shroud 38 is shown to comprise an internalintegral ring 39 carrying bearings 49 to allow the drill string to rotate Wi-thin and independently of the sleeve. Upward movement of the bit within the sleeve is limited by the engagement'of the sleeve Yshoulder V41 by a corresponding shoulder 42 on 1 lappropriate seal typified by the ring 46.

Above the shroud the sub or mandrel 21 carries a sleeve Fluid leakage past the lower end of4` the bearing ring 39, may be prevented by the use of an 47 connected by keys 48 so that the pipe string rotation is transmitted to the sleeve. The latter may carry aremovable outer sleeve segment 481 shouldered at 49.

VVSleeve 47 has a bottom counterboreSt which receives an appropriate bearing consisting typically of race rings 51 and V5,2 for'the ball bearings 53. Conned against ring Yshoulders 41 and 42, in which condition the bit is rotatable within the shroud. By lowering the drill string and y i sleeve 47 Yto the FIG. 3 position, the shroud is clutched (by the'interengagement of teeth 56 and projections 57 to rotate with bit and drill string. Y

For reasons p reviouslyrdiscussed, I prefer to maintain an appropriate barrier against excessive access of liquids In the FIG. 2

within the well bore, and therefore to transmission of Y excessive hydraulic heads, tothe bottorn'hole formation being drilled. For this purpose i may mount on the shroud: 38'one or more liexible packers 60 carried by sleeves 61 conlined between rings 62 and rotatable about the shroud 38, Vwhich rotation may be facilitated by the Vuse of roller bearings 63. Byfsuch packing means,'the

flow of liquid downwardly pastrthe packers may be limited to below the ratethat any bottom,V hole liquid becomes entrained in the circulating air stream.Y

In; considering the operation of the described embodiment, the apparatus may be assumed to be in the con- Ydition illustrated by FIG. 1, in which shroud 3S is bot-V t tomed in the hole.V

VYfurther lowered, spring 54 is compressed to exert a'down- As theV pipe or tubing string 1i is ward thrust against the shroud suiiicient to cause the shoe 44 toYV tend :toV penetrate the formation andA maintain ya pressure barrier between Ythe well' bore outside, and the shrourd'interior which dehnes the cutting locus kof the [bit cutters 2s.

(tend to Ymore or less'penetrate theformation, depending er upon its softness, and possibly to some. extent advance VUnder these conditions, the shroudmay i ahead of the bit; Normally, onwhen drilling harder Y fforrnations, the stringwill be lowering to clutch together the sleeve 47y and shroud 38 toV rotatably drive thejlatterV 'with the bit. Under these conditionsthebottom shoe 1.44 cuts and reafrn'sV the formation in relation tothe' cutting A area of the bit, while simultaneously the bit cuts out the center of the hole within `the shroud.

The bit cuttings are constantly released in exposure to the air streams jetted through passages 29 so that the cuttings become entrained in fthe air stream being returned to the ground surface through passages 37 and 24. In the presence of the barrier presented by the bit-body 23 and aided by the seal ring 46, it is possible to maintain relatively high air circulation pressure of several hundred p.s.i. inside the shroud, with the open hole or formation pressure being relatively low, say 50 p.s.i. In this manner assurance is given against excessive air loss to the well or formation, as well as troublesome vinterference with eiiicient entrainment of the cuttings by liquid intrusion into the working area of the bit.

FIG. 5 illustrates a variational'form of the invention in which the dual pipe string 162 and bit 163 have the same structure and association as the corresponding parts described in reference to FIGS. l to 4. Here fthe shroud sleeve 64 carries at its lower end the bottom shoe 65 and within its upper interior a circular series of ways 66 slideable upon splines 67 carried bythe drill string, sub or mandrel. During operation, the sleeve rotates with the bit and pipe string and is constantly urged downwardly into sealing engagement with the bottom hole formation by the weight of the shroud which, if desired, may be supplemented by coil spring 11K/confined between the pipe string-carried ring 68 and the upper endV of sleeve 64. The latter is shown to carry a packer 69 corresponding in structure and functions tothe previously described packers 60. packer 70 may be similarly carried directlyby the pipe string on sleeve 71 within which the string is rotatable, rings 72 serving to coniine the packer axially of the string.

In operation of the FIG. 5 embodiment, sleeve 64 is constantly rotated with the bit and urged downwardly by spring 67 to drill and ream the bottom hole formation aboutthe cutting area of the bit 163. Depending upon the hardness or drillability of the formation, the sleeve may tend to advance somewhat ahead of the bit, as illustrated, or the latter may operate whilerlowered to or even somewhat below the bottom cutting shoe of the sleeve. Y Y i Y I claim:

l. In combi-nation with well drilling apparatus compris? ing a rotatable dual pipe string including annularlyspaced inner and outer pipes defining between them an 'injection passage, the inner pipe containing a return passage, and a drill bit carried by theV lower end of said pipe string having cutters positioned in a fluid iiow path between said injectionpassage and said return passageso that huid may w be Vdelivered to therbit through said V,injection passageV and returnedV to the Vground surfacerwith bit cuttings through said return passage; aV tubular shroud surrounding the drill bitV and `adapted to Vengage the bottom hole formation v about VVtherbit as'drilling proceeds and thereby present a barrier' towell liuid interferencerwith'rsaid fluid being ref interconnecting the Vbitandshroud'fo'r rotation together.

4. The combination of claim l, including Valso means for selectivelyrotating and maintaining the shroud against rotation during the pipe StringrOtation.

5. The combination vof claim l, including also a cornpressor operating to deliver compressedair Vtosaid injection passage for entrainmentpoffthe bit cuttings in a .return air stream in said return passage., y' Y V6. The combination'of'claimfl, in which said shroud is movable relative to the'bit so that Vthe bit mayecutabove or below thelbottom ofthe shroud. A Y Y 7. The combination of claim 6, ingwhich tlie'bitfisV rotatable within the shroud',V and including 'also'rneans for' If desired, a supplemental upper releasably interconnecting the bit and shroud for rotation together.

8. The combination of claim 6, including also yielding means urging the shroud downward relative to the bit.

9. The combination of claim 1, including also packer means operable to engage the formation above said bit.

10. The combination of claim 9, in which said packer means is carried by the shroud.

11. The combination of claim 9, in which said packer means is carried by the pipe string above the shroud.

12. In combination with well drilling apparatus comprising a rotatable dual pipe string including annularly spaced inner and outer pipes defining between them an injection passage, the inner pipe containing a return passage, and a drill bit carried by a bottom section of said pipe string having cutters positioned in a fluid ow path in communication with said injection passage and said return passage so that iiuid may be delivered to the bit through said injection passage and returned to the ground surface with bit cuttings through said return passage; a tubular shroud surrounding said bottom section of the string and the drill bit, said shroud being vertically movable relative to the bit and being engageable with the bottom hole formation as drilling proceeds to impose a pressure barrier between the formation pressure and the pressure of the uid circulated to and from the bit through said passages- 13. The combination of claim 12, in which said pipe string section is rotatable within the shroud.

14. The combination of claim 12, including also yield- 3 ing means urging the shroud downward relative to the bit.

15. The combination of claim 12, including also a compressor operating to deliver compressed air to said injection passage for entrainment of the bit cuttings in a return air stream in said retur-n passage.

16. The combination of claim 12, including also means interconnecting said section and shroud for rotation together.

17. The combination of claim 16, in which said interconnecting means is releasable to allow the shroud to remain rotationally stationary during drilling.

18. The combination of claim 16, including also packer means above the bit and adapted to engage the Well bore wall.

References Cited in the ile of this patent UNITED STATES PATENTS 1,018,333 Meyer Feb. 20, 1912 2,022,101 Wright Nov. 26, 1935 2,234,454 Richter Mar. 11, 1941 2,323,027 Gerstenkorn June 29, 1943 2,663,545 Grable Dec. 22, 1953 2,696,367 Robishaw Dec. 7, 1954 2,786,652 Wells Mar. 26, 1957 2,815,930 Storm Dec. 10, 1957 2,849,214 Hall Aug. 26, 1958 2,894,727 Henderson July 14, 1959 2,914,306 Failing Nov. 24, 1959 2,942,667 Blood et a1 June 28, 1960 2,994,389 Le Bus Aug. l, 1961 

1. IN COMBINATION WITH WELL DRILLING APPARATUS COMPRISING A ROTATABLE DUAL PIPE STRING INCLUDING ANNULARLY SPACED INNER AND OUTER PIPES DEFINING BETWEEN THEM AN INJECTION PASSAGE, THE INNER PIPE CONTAINING A RETURN PASSAGE, AND A DRILL BIT CARRIED BY THE LOWER END OF SAID PIPE STRING HAVING CUTTERS POSITIONED IN A FLUID FLOW PATH BETWEEN SAID INJECTION PASSAGE AND SAID RETURN PASSAGE SO THAT FLUID MAY BE DELIVERED TO THE BIT THROUGH SAID INJECTION PASSAGE AND 